1. Field of the Invention
This invention pertains to the field of tooling. More particularly, this invention pertains to hand tools and to a powered hand tool for applying wire ties or clips to the intersections of tubular elements, such as concrete rebars and the like, so that the rebar structure becomes tightly bound together before concrete is poured thereover.
2. Description of the Prior Art
Man has been building large structures throughout history. First came the monolithic structures such as the famous heads of Easter Island. Later came the pyramids and the Great China Wall. All of these structures were made of individual pieces of natural stone that were carefully cut and modified to fit tightly together as a whole structure.
These structures required many persons and many days, weeks, months and, in some cases, years of work to complete. Even then, earth quakes and general settling of the earth caused many of these structures to sag and/or collapse. These structural failings were mainly caused by the inability of the structure to retain its structural integrity on the shifting earth.
It is believed that the Greeks and Romans first discovered concrete. Concrete is a mixture of sand and gravel bonded together with cement. Cement is the product of burnt lime and clay. By adding water to the mixture, it may be made fluid and poured into a form or mold to take many shapes.
In the early 1900's, it was discovered that if one placed a very strong matrix inside a molded structure of cement, then any load from the exterior of the structure was passed through the cement to the matrix. This was exemplified by erecting strong steel bars inside a form and then pouring concrete over the bars. The final structure, known as "steel reinforced concrete" was able to withstand loads many times greater than the loads that would cause failure to non-reinforced concrete.
The patent history of reinforced steel concrete can be gauged by the issuance of patents for improvements in the reinforcing structures. For instance, U.S. Pat. No. 1,637,742 discloses the use of metal "chairs" at points of intersection of the steel reinforcing rods, called "rebars". This tying together of the rebars improved the overall integrity of the matrix and increased the load stability of the final concrete structure.
U.S. Pat. Nos. 1,816,833; 2,298,104; 3,16:3,266; 4,005,560; 4,388,791; 4,939,883; and, British Patent 589,447 all disclose physically applied metal wires or clips to rebar structures to enhance the overall integrity of the reinforcing matrix to produce a stronger concrete structure. There are some items of interest in this history. For instance, all these patents disclose wire ties and clips that are physically tied to the rebars. There are no patents that discuss welding the rebars together at their points of intersection. The reason is that welding changes the hardness and other physical properties of the rebars in the area of the weld and those changed physical properties are quite detrimental to the loadbearing quality of the overall structure.
While tying the rebars together takes wire, it is common to use the word "clip" when discussing ties that are made of strong wire. In this patent application, the inventor has chosen the word "clip" to mean the metal wire that is wound about the rebar to connect two or more rebars together as they pass in tangential contact with each other.
Typical of the wire clips disclosed in the patents is U.S. Pat. No. 4,388,791 that discloses a clip that is applied by hand to the intersection of rebars in the structure and that is able to be loosened by tilting upward to partially remove the legs of the clip from the overlapping rebars. All the patents set out above disclose rebar clips that are applied by hand. This is a very arduous and time-consuming process. In addition, it is costly because of all the manual labor expended by those who cut, shape, apply, and twist the clips about the intersecting rebars to form the connection therebetween. Up to the present, there has not been a machine nor other appliance developed that would allow the wire clips to be applied to the intersections of the rebars using other than hand power.